How can i remove none alphabet chars from a string[]? [duplicate]

Answer 1

To help Konrad and keyboardP resolve their differences, I ran a benchmark test, using their code. It turns out that keyboardP's code is 10x faster than Konrad's code

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Text.RegularExpressions;

    namespace ConsoleApplication1
    {
        class Program
        {
            static void Main(string[] args)
            {
                string input = "asdf234!@#*advfk234098awfdasdfq9823fna943";
                DateTime start = DateTime.Now;
                for (int i = 0; i < 100000; i++)
                {
                    RemoveNonUnicodeLetters(input);
                }
                Console.WriteLine(DateTime.Now.Subtract(start).TotalSeconds);
                start = DateTime.Now;
                for (int i = 0; i < 100000; i++)
                {
                    RemoveNonUnicodeLetters2(input);
                }
                Console.WriteLine(DateTime.Now.Subtract(start).TotalSeconds);
            }
            public static string RemoveNonUnicodeLetters(string input)
            {
                StringBuilder sb = new StringBuilder();
                foreach (char c in input)
                {
                    if (Char.IsLetter(c))
                        sb.Append(c);
                }

                return sb.ToString();
            }
            public static string RemoveNonUnicodeLetters2(string input)
            {
                var result = Regex.Replace(input, "\\P{L}", "");
                return result;
            }
        }
    }

I got

0.12
1.2

as output

UPDATE:

To see if it is the Regex compilation that is slowing down the Regex method, I put the regex in a static variable that is only constructed once.

            static Regex rex = new Regex("\\P{L}");
            public static string RemoveNonUnicodeLetters2(string input)
            {
                var result = rex.Replace(input,m => "");
                return result;
            }

But this had no effect on the runtime.